improve Q.of_string to make it handle decimal point and scientific notation

ocaml / Zarith

The Zarith library implements arithmetic and logical operations over arbitrary-precision integers and rational numbers. The implementation, based on GMP, is very efficient.

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improve Q.of_string to make it handle decimal point and scientific notation #65

Closed ghilesZ closed 5 years ago

ghilesZ commented 5 years ago

This PR implements the handling of decimal point number (eg, 3.14) and scientific notation (eg, 6,674 30e−11)in Q.of_string, as requested by issue#10 (Underscores are however still not uderstood). It also adds the testing of the new features in tests/ofstring.ml test files.

The implementation is in regular OCaml (no C or assembly code is used), and performs computations that can be a bit redundant with Z.of_string (parsing of sign prefix and base prefix). These computations should maybe be put in common in future but i think this is a minor detail.

antoinemine commented 5 years ago

Thanks !

hhugo commented 4 years ago

I believe the implementation is not correct.

the exponent in the hexadecimal notation is parsed in base 16, but it should be parsed in base 10
hexadecimal notation containing radix and exponent are not handled correctly 0x1.1p1 should be 2.125 but is parsed as 17.

ghilesZ commented 4 years ago

Oups i didn't know that. Also it seems that in hexadecimal notation, exponents are written in decimal, but should be interpreted as powers of two as 2.125 = 0x1.1 * 2^1. I can work on a fix.

ghilesZ commented 4 years ago

Do we agree that we should follow OCaml's lexical conventions?

antoinemine commented 4 years ago

Yes, it would be nice! Btw, we should check that Z.to_string is also complete (does it support underscores ?).

hhugo commented 4 years ago

Fyi, I've rewritten Q.of_stirng in #72